I thought I would unearth this post in the event that this particular problem happens to someone else in the future. I ran a search, and found nothing specifically like it, so I thought the following information might be of help in the future...
I ended up having to take the car to the dealer for diagnosis and repair. The problem turned out to be that the battery had leaked down underneath the tray and shorted some of the wires in the large harness under there. No parts were involved, just a bit of labor, so the bill wasn't too bad.
I had recently replaced the stereo, and wondered if I had somehow buggered the wiring while messing around in there, since the amp is so close to the PATS module; but it turned out to be a short in a completely different location. I spent many hours under the dash with a multimeter to no avail.
All the documentation I could find (including a couple Ford wiring schematics) led me to believe the circuit never ran up the battery and back, but that is apparently not the case.
Hoping this might help save someone a trip to the dealer if the car is throwing a blinking PATS code. CEG has always been a valuable resource for me, and one of the ways to perpetuate this is for myself and others to post solutions as well as questions. My thanks to the community for all the help.
